Continuous process and apparatus for pulping fibrous materials



Dec. 12, 1933.

C. E. BRAUN ET AL CONTINUOUS PROCESS AND APPARATUS FOR PULPING FIBROUSMATERIALS Filed April, 19, 1932 4 Sheets-Sheet l HIMER a dzgZZZ reJ-Halrer unddeqy 5' Dec. 12, 1933. E. BfiAUN ET AL 3 com muons PROCESSAND APPARATUS FOR PULPING FrBRous MATERIALS Filed April 19, 1952 4Sheets-:Sfieet 2 De.'12,1933. CQ-EFBRAUN ETAL 1,938,802.

CONTINUOUS PROCESS AND APPARATUS FOR PULPING FIBROUS MATERIALS FiledApril 19, 1932 4 Sheets-Sheet 3 AND C' E-flraun A: Huh grime];

Dec-- 12, 1933.

C. E. BRAUN ET AL CONTINUOUS PROCESS AND APPARATUS FOR PULPING FIBROUSMATERIALS 'Filed A ril- 19, 1952 4 Sheets-Sheet 4 m M MH AND da'lPatented Dec. 12, 1933 UNITED "STATES con'mmous morass m maaa'rus roarmrmo muons MATERIALS York Application April 19, 1932. Serial No.606,255

This invention relates to improvements in processes and apparatus fordigesting fibrous mateferent units of the apparatus, and by which the.fibrous material may be washed in one unit after V it has been digestedin a previous unit with one kind of chemical liquor, and before it isdigested in a following unit with another kindof chemical liquor.

With the foregoing objects outlined and with other objects in view whichwill appear as the description proceeds, the invention consists in thenovel features hereinafter described in detail, illustrated in theaccompanying drawings, and more particularly pointed out in the appendedclaims.

In the drawings,

Fig. 1 is a diagrammatic view of the complete apparatus.

Fig. 2 is a side elevation partly in section, oil the first two units ofthe apparatus and their associated equipment.

Fig. 3 is an elevation of the last two units of v the system and theirassociated equipment.

Fig. 4 is a vertical sectional view on the line 4-4 of Fi '2.

Fig. 5 is a diagrammatic view of an electric device for controlling theapparatus.

Fig. 6 is a similar view of the wiring arrangement of such apparatus.

Referring first to Fig. 1, it will be noted that the apparatus consistsof a number of units or closed drums 6, 7, 8, 9 and 10, arranged in Iseries.

1 ing up of chips and cooked pulp, and is provided with a pair of valves18 and 19 to permit feeding of material through the system withoutaffecting the temperature'or pressure conditions existing in any one ofthe units.

The fresh treating liquor is introduced into the units by way of valvedpipes 20, and of course, if the same kind ofcooking liquor is to .beused in two or more of the units, the pipes 20 may be connected to acommon header through which the liquor flows.

The liquor introduced at 20 into each unit 6,

7, 8. and 9, is forced by a pump 21 through an indirect heater 22, andafter it is heated, it passes by way of a valved pipe 23 into the upperportion of the unit. Liquor'is drained from each unit into arecirculating pipe 24 whichmay return some or all of it to the pump ofthat unit. We prefer, however, to provide each pipe 24mm 9. valvedoutlet 25 to allow discharge; of some or all of the treating liquor whendesired.

All of the heaters 22 are connected by valved branch pipes 26 to a steamheader 27, and the lower ends of the heaters are connected by valvedbranches 28 to a condensate header 29 that may be used for returning thehot condensate back to the steam generating boiler (not shown).

As indicated in Fig. 2, each of the units or drums is provided with arotatable worm or feeding screw 30, and these worms are positioned onrotatable shafts 31, and driven through the instrumentality of reductiongearing 32 by an electric motor 33. All'of these motors may receivecurrent from lead wires 34 and 35.. Each worm, as indicated in'Fig. 2,is perforated as at 36 to permit circulation of the treatingliquorthrough the drum, and each drum is provided near its outlet endwith a weir 3'? over which the fibrous material is forced by the worm.

The valves 18 and 19 may be controlled by any suitable means, forexample, by the device illustrated in Figs. 5 and 6. In thisarrangement, the shaft 31 of the second cooker is provided with asprocket wheel that drives a sprocket chain 76. This chain in turndrives a sprocket wheel '77, fixed to a shaft 78. This shaft carriespairs of contact disks or wheels 79 and 80, and the num- 1 her of pairscorresponds to the numbers of the valves 18 and 19. Each of these valvesis provided with a piston81, operating in a steam cylinder 82. Steam isfed'to the cylinder through a pipe 83, and the exhaust steam returns tothe 1 heater (not shown), by means of a pipe 84. A rocking valve 85controls the feed'and discharge of steam, and the lever 86 of this valvemay be moved in opposite directions by solenoids 8'1 and 88 interposedin electric circuits which are opened and closed by the contactor wheels79 and 80.

' and this is accomplished by It will be understood that when thecontactor wheel 79 closes the circuit through the solenoid 87, the valve85 will be moved in one direction, and when the contactor wheel closesthe circuit through the solenoid 88, the valve will be moved in theopposite direction. I

By the use of such a control mechanism, it will be evident that all ofthe valves 18 and 19 throughout the system, may be operated in propersequence.

Referring to the operation of such apparatus, it will be noted that thevalve 12 is of the rotatable type, and it may be constantly orintermittently rotated for automatically feeding the chips or the likeinto the pipe 11. As this automatic chip feeder is divided intoquarters, two sides are open and two sides are closed. As the valverevolves, one of its chambers fills with a determined amount of thefibrous material to be cooked, and as the valve revolves, this amount isdischarged into the pipe 11 and on top of the sliding valve 18. Thisvalve then opens while the second valve 19 remains closed to hold thepressure in the first chamber or unit 6. After the first valve hasdischarged its burden, it closes, and then the second valve opens anddischarges the chips into the first unit 6. At this point it will benoted that the measuring valve 12 and the first and second valves 18 and19 of each of the conduits are operated in a definite sequence, eitherby hand or by an automatic control shown in Figs. 5 and 6.

After the valve 19 dumps its burden into the unit 6, this valve closes.

A determined amount of fresh hot cooking liquor is added by way of pipe20 during each opening of the second valve- 19. This liquor enters justback of the circulating pump21 which draws the liquor out of the side orbottom of the unit. The pump discharges to the high velocity heater 22,and the hot liquor leaves this heater and is admitted to the head of theunit 6 just below the valve 19.

The chips or other fibrous material in the continuous cooker 6 areslowlymoved from the entering end of the cooker to the discharge end, the wormor slowly revolving screw 30. The worm may have in addition to theperforations, blades 41 to agitate the material undergoing cooking.

Such worm conveyor is driven at a relatively slow speed by the directcurrent motor 33 throughthe reduction gear set 32. It has been foundbest to use a direct current motor as it permits better speed regulationand a wider range of speeds. We recommend the use of a standard papermachine electric drive, as this gives better regulation between thecookers, and also group speed range.

Each unit 1: rs on its shell, outlets conveniently arranged for theattachment of temperature and pressure gauges 42 and 43. Provision isalso made at the outlet end of each unit, as indicated at 44, with theexception of the last one,

. for the connection of a gas relief line.

sage of gases through such lines may be regulated The pasby suitablecontrol means responsive to sure existing in the units.

the pres- During operation, the chips or other fibrous materials aremoved forward until they reach the outlet end of the cooker, and thenthey are forced over the top of the bulkhead 37 with a certain amount ofliquor and dropped on top of the valve 18 in the conduit 14. At thistime, both valves 18 and 19 in the conduit 14 are closed. When adetermined amount of the partly cooked contents and liquor are depositedon the valve, 18, it is opened and this amount is dropped on to thevalve 19, after which the valve 18 of this conduit is closed. Then, whenthe valve '19 of such conduit is opened, this partly cooked material andsuch liquor are dropped into the unit 7, which can be actuated at ahigher or lower pressure than exists in the unit 6. g

The operation fromhere on is exactly the same for each cooker,regardless of how many cookers are used,and also regardless of thepressure existing in the various cookers.

The last unit 10 which may be called the dis-, charge drum, is the sameinternally as the previous ones, but it has a row of inlets 45 at itstop to admit water from a manifold 46 for the purpose of condensingsteam, gases, etc. The bottom has a row of outlets 47 joined to adischarge manifold 48 which can be used to drain the liquor forreclaiming if necessary. By arranging suitable valves 49 and 50 in thedischarge conduit 5011, the unit 10 can be kept under pressure ifdesired.

From the pipe. 50a, the stock is dumped continuously into a chest orover a washer, and thence to a knotter and the conventional riiilers,flat screens, etc.

In operating the apparatus, we prefer to drive the worm conveyor of theunit 6 faster than the worm of the unit 7, and so on. The reason forthis is that as the chips cook down, we want to keep each cooker as fullas possible for ,best results.

This system, regardless of size, can be controlled by a single operatorfrom the chip bin to the screens. In commercial operation, an

visible glass on the board before it is returned] to the cooker. A draincock may also be placed below each such indicator for sampling andtesting. A cock may also be used for testing the fresh cooking. liquor.It is also advisable to have the shift pulp tester located at suchcontrol board, so as the pulp comes out of the last unit, the observercan immediately give his results to the man in charge of the cookers.

In actual practice, we intend to pass the relief fluids'from theconnections 44 to an accumulator containing acid. liquor for the purposeof preheating and preconditioning such liquor. Such accumulator willhave a heater attached so that the liquor drawn of! for the cookers willalways be of the same temperature. Consequently, the heater 22- of anyparticular unit, will heat the preheated liquorup to the desiredtemperature. The temperature of each liquor heater is kept constant bythe use of proper temperature controls and thermometers controlling theamount of steam entering the heater through the pipe 26. Such a controlis indicated diagrammatically at 51.

With this system, it is possible to maintain positive pressures andtemperatures in each cooker regardless of the temperature and pressureexisting in any other cooker, and to still be able to admit the materialundergoing cooking from one chamber to the next without disturbing theindividual pressures and temperatures. Furthermore, this system has theadvantage of making any class of pulp possible, simply by changing thecooking time and the strength of the cooking liquor. This it is possibleto do instantaneously.

In addition, this system will make a far superior grade of Mitscherlich'pulp. The pulp will always be uniform, and a greater yield of pulp perton of raw material can be obtained.

It is also possible with our apparatus to reclaim the liquor for furtherrefining and reuse. Due to the indirect method of heating which weemploy, the cooking liquor will not be diluted with condensed steam,andconsequently, the cooking time can be shortened. By using externalheaters, the steam consumption is lowered, as the condensate from theheaters can be returned to the steam plant for direct admission to theboilers.

There would be no objection to having our system located in theimmediate vicinity of any town, as there are no gases to liberate to theatmosphere, as they. are condensed in;the last unit 10, and suchcondensation may be carried out continuously.

The metal of each cooker can be made of the proper'material to withstandthe corrosive action of the cooking liquor.' Chromium nickel steels thatare now available are highly resistant to the acids and alkalis used inproducing chemical pulp. Therefore, our method is feasible from thepoint of materials available for the construction of the apparatus, andfurthen'the complete cost of a large daily' tonnage plant will be verymuch smaller-than plants in use today, particularly as the sulphiteprocess, when practiced with our system, will not require the use of anyacidproof lining, and the system for this purpose can be built in suchsmall units that it is easily constructed of available materials. Itwould be impossible to build a sulphite digester of the sizes nowcommonly used of chrome nickel steel, as it would be impossible to heattreat such chrome nickel steel after the digester was erected.Therefore, all prior digesters are constructed of flange steel platesriveted together and lined with an acid-proof lining. Drums, inaccordance with our invention, do not require any acid-proof lining, andas the system has large capacity, even with the use of small units, theapparatus is very economical and uses up less space.

If desired, the same cooking drums can be applied to bleaching, as ourconstruction makes it possible to use the most injurious chemicals withno drastic effects to the operators.

It will also be observed that we effect a saving in initial cost, asitis unnecessary to have more than one chip bin, and this need only holdan amount equal to about half the capacity of one of the units at anyonetime.

There are no blow pits to take care of in our system with a loss of goodstock through the drainer bottoms. This system will be of considerableadvantage in the newtwo, liquor process which has promises of cookingDouglas fir, using the sulphate or soda liquor first. then washing inone of the chambers, and continuing the cooking bythe sulphite processin one or more of the following units. In such operation, some of theunits are used as sulphate cookers, and the sulphate liquor is drawn oiffrom those units for reclaiming. Then the stock is washed in asucceeding unit and after that it is put through the sulphite process ina later unit or units. There is no limit'to the possibilities thissystem has in any liquor combination.

This method of cooking and our apparatus also can be used in cookingeither sulphite, soda, sulphate, or kraft pulp. In fact, it can be usedfor any chemical method of pulpingmaterial containg cellulose. I

While'we have described our process and apparatus in such manner thatthey may be read-.- ily uiiderstoodby those skilled in the art, we areaware that changes may be made in .the details disclosed, withoutdeparting from the spirit of the invention, as expressedin the claims.

What we claimand desire to secure by Letters Patent is:

1. A continuous process for the chemical pulping of fibrous materials,comprising feeding the material through a plurality of superposeddigesting chambers, subjecting the material in each chambr to contactwith a heated chemical liquor, maintaining the material in each chain- 4her at a determined pressure independently of the pressure existing inthe other chamber, and dropping the material from the upper to the lowerchamber.

7 2. A continuous process for the chemical pulping of'fibrous materials,comprising feeding the material through a plurality of superposeddigesting chambers, subjecting the material in each chamber to contactwith a heated chemical liquor, maintaining the material in each chamberat a determined pressure independently oi the pressure existing in theother chamber, dropping the material from the upper to the lower chamberand circulating the chemical liquor through the fibrous material in eachchamber.

3. A continuous process for the chemical pulping of fibrous materials,comprising feeding the material through a plurality of digestingchambers, subjecting the material in each chamber to contact with aheated chemical liquor, maintaining the material in each chamber ata'determined pressure independently of the pressure existing in theother chamber, and circulating the chemical liquor in an endless pathand through the fibrous material in each chamber.

4. A continuous process for the chemical pulping of fibrous materials,comprising feeding the material through a plurality of digestingchambers, subjecting the material in each chamber to contact with aheated chemical liquor, main-- taining the material in each chamber at apredetermined pressure independently of the pressure existing in theother chamber, circulating the chemical liquor in an endless path andthrough the material in each chamber, and heating the liquor in itstravel along said endless pat 5. A continuous process for the chemicalpulping of fibrous materials, comprising feeding the material through aplurality of digesting cham- L bers, subjecting the material in eachchamber to contact with a heated chemical liquor, maintaining thematerial in each chamber at a deter mined pressure independently of thepressure ing of fibrous materials, comprising feeding the materialthrough a plurality of digesting chambers, subjecting the material ineach chamber to contact with a heated chemical liquor, maintaining thematerial in each chamber at a determined pressure independently of thepressure existing in the other chamber, and indirectly heating thechemical liquor exteriorly of the chamber before chamber.

'l. A continuous process for the chemical pulping of fibrous materials,comprising feeding the material through a plurality of digestingchambers, subjecting the material in each chamber to contact with aheated chemical liquor, maintaining the material in each chamber at apredetermined pressure and temperature independently of the pressure andtemperature existing in the other chamber, and circulating the chemicalliquor through the fibrous material in each chamber while the fibrousmaterial is moving through the chamber.

8. A continuous process for the chemical pulping of fibrous material,comprising feeding the material through a plurality of digestingchambers, subjecting the material in each chamber to contact with aheated chemical liquor, maintaining the material in each chamber at adetermined pressure independently of the pressure existing in the otherchamber; circulating the chemical liquor in an endless path and throughthe material in each chamber while the fibrous material is movingthrough the chamber, and heating the liquor exteriorly of the chamberwhile the liquor is circulating in said endless path.

9. A continuous method of chemically pulping fibrous material,comprising positively moving such material through a digesting chambermaintained under super-atmospheric pressure, adding raw fibrous materialsubstantially continuously to the inlet end of said chamber, dischargingmaterial which is at least partially cooked substantially continuouslyfrom the outlet end of the chamber, circulating hot chemical liquor at apredetermined temperature in an endless path and through the chamberwhile the fibrous material is being nioved through the chamber, andheating the liquor exteriorly of the chamber.

10. A continuous method of chemically pulping fibrous material,comprising positively moving such material through a digesting chambermaintained under super-atmospheric pressure, adding raw fibrous materialsubstantially continuously to the inlet end of said chamber, dischargingmaterial which is at least partially cooked substantially continuouslyfrom the outlet end of the chamber, circulating hot chemical liquor inan endless path and through the chamber while the fibrous material isbeing moved through the chamber, and continuously heating the chemicalliquor exteriorly of the chamber as it travels in said endless path. a

11. A continuous method of chemically pulping fibrous material,comprising positively moving such material through a digesting chambermaintamed under super-atmospheric pressure, adding raw fibrous materialsubstantially continuously to the inlet end ofsaid chamber, dischargingmaterial which is at least partially cooked substantially continuouslyfrom the outlet end of the chamber, circulating hot chemical liquor. inan endless path and through the chamber while the fibrous material isbeing moved through the chamber, and continuously heating the chemicalliquor indirectly and exteriorLv of the chamber I introducing the liquorinto the while the liquor circulates in said endless path.

12. A continuous method of chemically pulping fibrous material,comprising positively moving such material through a digesting chambermain-v tained under super-atmospheric pressure, adding raw fibrousmaterial substantially continuously to the inlet end of said chamber,discharging material which is at least partially cooked substantiallycontinuously from the outlet end of the chamber, circulating hotchemical liquor in an endless path and through the chamber while thefibrous material is being moved through the chamber, and indirectlyheating the chemical liquor exteriorly oi the chamber while the liquorcirculates in said endless path.

13. A continuous method of chemically pulping fibrous material,comprising positively moving such material through a digesting chambermaintained under super-atmospheric pressure, adding raw fibrous materialsubstantially continuously to the inlet end of said chamber, dischargingmaseparate from the hot liquor.

15. A process for chemically pulping fibrous material, comprisingintroducing cooked fibrous material and cooking liquor in hot conditioninto a chamber, introducing a combined washing and cooling fiuid intothe chamber for cooling the fibrous material to a predeterminedtemperature and condensing any gases or vapors tending to separate fromthe hot liquor, and continuously moving the fibrous material throughsaid chamber while it is subjected to the cooling and washing fluid.

16. In a process of the character described, positively andsubstantially continuously moving a stream of fibrous material through achamber, simultaneously circulating a chemical treating liquor in anendless path through the material in said chamber, and heating saidliquor exteriorly of the chamber without mixing steam with the liquor.

17. In a process of the character described,

positively and substantially continuously moving said liquor exteriorlyof the chamber without mixing steam with the liquor.

18. In the chemical pulping of fibrous material, feeding said fibrousmaterial through a series of superposed chambers, cooking said materialin the first chamber with a hot chemical cooking liquor, then droppingthe material into a lower cm of the chambers and cooking said materialsubsequently in the last mentioned one of the chambers with a difierentkind of chemical cool:-

ing liquor. q

19. In the chemical pulping of fibrous material,

feeding such material through a series of cham- 1 bers, cooking thematerial inthe first one 01' the chambers with a chemical cookingliquor, afterwards washing the material in a succeeding one of thechambers with a washing liquid, and afterwards again cooking the fibrousmaterial in a further one of the chambers with a different kind orchemical cooking liquor than that used in the first chamber.

20. In the chemical pulping of fibrous material, continuously feedingsuch material through a series of connected chambers, circulating a hotchemical cooking liquor through the first chamber while the material ispassing through the I same for initially cooking the material, washingthe material with a washing liquid while the materialis passing througha second chamber otthe series, and cooking the material in a thirdchamber of the series by circulating a hot difierent kind or chemicalliquor through said third chamber while the fibrous material is passingthrough the third chamber.

21. An apparatus for digesting fibrous material, comprising 'a series ofchambers, each having an inlet and an outlet, conduits connecting theoutlets of certain of the chambers to the inletsof certain of the otherchambers, valves in said conduits for maintaining the pressure in eachchamber independently of the pressure existing in any other one of thechambers, a conveyor in each chamber, and means for introducing a'treating liquor into each chamber and for discharging said liquor fromthe chamber.

22. An apparatus for digesting fibrous material, comprising a series ofchambers, each having an inlet and an outlet, conduits connecting theoutlets of certain of the chambers to the inlets of certain of the otherchambers, valves in said conduits for maintaining the pressure in eachchamber independently of the pressure existing in any other one of thechambers, a conveyor in each chamber, and means for introducing atreating liquor into eachchamber and for discharging said liquor fromthe chamber, each conveyor being provided with means to permit thepassage of liquor through the same.

' 23. An apparatus for digesting fibrous material, comprising a seriesof chambers, each having an inlet and an outlet, conduits connecting theoutlets of certain of the chambers .to the inlets of certain of theother chambers, valves in said conduits for maintaining the pressure ineach chamber independently of the pressure existing in any other one ofthe chambers, a conveyor in each chamber, and means for introducing atreating liquor into each chamber and for discharging said liquor .fromthe chamber, each conveyor being in the form of a rotatable worm.

24. An appartus for digesting fibrous material, comprising a series ofchambers, each having an inlet and an outlet, conduits connecting theoutlets of certain of the chambers to the inlets of certain of the otherchambers, valves in said conduits for maintaining the pressure in eachfor driving the conveyor of each chamber at a different-speed from thatof a conveyor of another one of the chambers.

25. An apparatus for digesting fibrous material, comprising a series ofchambers, each having an inlet and an outlet, conduits connecting theoutlets of certain of the chambers to the inlets oi certain of the otherchambers, valves in said conduits for maintaining the pressure in eachchamber independently of the pressure existing in any other one of thechambers, a conveyor in each chamber, means for introducing a treatingliquor into each chamber and for discharging said liquor from thechamber, and a weir in each chamber near the outlet end of the same.

26. An apparatus for digesting fibrous material, comprising a series ofchambers, each having an inlet and an outlet, conduits connecting theoutlets. of certain of the chambers to the inlets of certain of theother chambers, valves in said conduits for maintaining the pressure ineach chammeans including a pump for circulating the liquor.

- 2'7. An apparatus for digesting fibrous material, comprising a seriesof chambers, each-having an inlet and an outlet, conduits connecting theoutlets of certain of the chambers to the inlets of certain of the otherchambers, valves in said conduits for maintaining the pressure in eachchamber independently of the pressure existing in another one of thechambers, a conveyor in each chamber, and means for introducing atreating liquor into each chamber and for discharging said liquor fromthe chamber, the last mentioned means including a circulating pump and aheater for the liquorl 28. An apparatus for digesting fibrous material,comprising a series of chambers, each having an inlet and an outlet,conduits connecting the outlets of certain of the chambers to the inletsof certain of the other chambers, valves in said conduits for,maintaining the pressure in each chamber independently of the pressureexisting in any other one of the chambers, a conveyor in each chamber,means for introducing a treating liquor into each chamber and fordischarging said liquor from the chamber, and means for venting gasesand vapors from certain of the chambers. 1

29. An apparatus for digesting fibrous material, comprising a series 01'chambers, each having an inlet and an outlet, conduits connecting theoutlets of certain of the chambers to the inlets of certain of the otherchambers, valves in said conduits for maintaining the pressure in eachchamber independently of the pressure existing in any other one of thechambers, a conveyor in each chamber, and means for introducing atreating liquor into each chamber and. for discharging said liquor fromthe chamber, the valves. being arranged in pairs in'each oi theconduits.

30. An apparatus for digesting fibrous material, comprising a series ofchambers, each having an inlet and an outlet, conduits connecting theoutlets of certain of the chambers to the inlets of certain of the otherchambers, valves in said conduits for maintaining the pressure inforintroducing fibrous material into said pipe.

31. An apparatus of the classdescribed, comprising a stationary closedchamber having an inlet at one end and an outlet at its opposite end, amovable conveyor in the chamber for feeding fibrous material through thechamber from the inlet to the outlet, a heater, a pipe placing theheater in communication .with the chamber, a second pipe for withdrawingcooking liquor from the chamber, and means for forcing liquor from thelast mentioned pipe through the heater and into the first mentionedpipe.

32. An apparatus of the class described, comprising a stationary closedchamber having an inlet at one end and an outlet at its opposite end, amovable conveyor in the chamber for feeding fibrous material through thechamber from the inlet to the outlet, a heater, a pipe placing theheater in communication with the chamber, a second pipe for withdrawingcooking liquor from the chamber, means for forcing liquor from the lastmentioned pipe through the heater and into the first mentioned pipe, aninlet conduit connected to the inlet of the chamber, an outlet conduitconnected to the outlet of the chamber, and a pair of valves in tandemarrangement interposed in each of said conduits.

33. An apparatus of the class described, comprising a stationary closedchamber having an inlet at one end and an outlet at its opposite end, amovable conveyor in the chamber for feeding fibrous material through thechamber from the inlet to the outlet, a heater, a pipe placing. theheater in communication with the chamber, a second pipe for withdrawingcooking liquor from the chamber, means for forcing liquor from the lastmentioned pipe through the heater and into the first mentioned pipe, andmeans for rotating said conveyor. v

34. An apparatus of the character" described, including a closed chamberhaving an inlet at one end and an outlet at its opposite end, a movableconveyor in the chamber for moving fibrous material through the chamberfrom its inlet to its outlet, a manifold having branch pipes con-,nected to the top of the chamber at spaced points along the length ofthe chamber, and a liquor discharge pipe having branches connected tothe bottom of the chamber at spaced points along the length of thechamber.

35. An apparatus for digesting fibrous material, comprising a series ofchambers, each having an inlet and an outlet, conduits connectingtheoutlets of certain of the chambers to the inlets of certain of theother chambers, valves in said conduits for maintaining the pressure ineach chamber independently of the pressure existing in any other one ofthe chambers, and means for alternately operating the valves in each ofsaid conduits.

36. An apparatus for digesting fibrous material, comprising a series ofchambers, each having'an inlet and an outlet, conduits connecting theoutlets of certain ofthe chambers to the inlets of certain of the otherchambers,. valves in said conduits for maintaining the pressure in eachchamber independently of the pressure existing in any other one of thechambers, and

means for alternately operating the valves in each of said conduits, thelast mentioned means comprising a pressure fluid operated piston.

37. An apparatus for digesting fibrous material, comprising a series ofchambers, each having an inlet and an outlet, conduits connecting theoutlets of certain of the chambers to the inlets of certain of the otherchambers, valves in said conduits for maintaining the pressure in eachchamber independently of the pressure existing in any other one of thechambers, and means for alternately operating the valves in each of saidconduits, the last mentioned means including an electric circuit, asolenoid interposed in said circuit, a valve actuated by the solenoid,and a movable contact element for opening and closing said circuit.

38. An apparatus for digesting fibrous material, comprising a series ofchambers, each having an inlet and an outlet, downwardly flared conduitsconnecting the outlets of certain of the chambers to the inlets ofcertain of the other chambers, valves in said conduits for maintainingthe pressure in each chamber independently of the pressure existing inany other one of the chambers, a conveyor in each chamber, and means forintroducing a treating liquor into each chamber and for discharging saidliquor from the chamber.

' CARL E. BRAUN.

ALRIK H. LUNDBERG.

